A rotary electric machine is mounted on an electric vehicle or the like. In the rotary electric machine, it is necessary to cool a coil arranged in a stator in order to prevent performance deterioration due to heat generation thereof.
As a cooling structure of the stator, a coolant dropping type cooling structure is known in which a coolant is dropped from a coolant pipe disposed above the stator to a coil end of the stator, and the coolant spreads on the coil end to cool the stator.
In the coolant dropping type cooling structure, the coolant spreads following the shape of the coil due to gravity, and thus the lower side of the coil cannot be cooled, which results in a large temperature distribution in the coil. In particular, in a stator coil constituted by connecting many segment coils, the structure is different between a coil end provided on one end side of the stator core and a coil end provided on the other end side, so that the temperature distribution in the coil may be particularly large on either side. Therefore, it is conceivable to increase the flow of the dropping coolant to ensure the cooling performance. However, increasing the capacity of a pump for supplying a coolant causes increase in the weight of the pump, increase in energy consumption, increase in the number of coolant dropping pipes, and the like, which increases the cost.
Another cooling structure of a stator is an axial cooling structure. JP-A-2011-142788, for example, discloses that a first discharge hole is formed in a coolant flow path provided between a wall surface of an end plate and an end surface of a rotary core, and a discharge groove having a second discharge hole is formed in a circumferential shape on an outer circumferential side of the coolant flow path, so that the coil is cooled by the coolant discharged from the first and second discharge holes.
In the cooling structure of an electric motor of JP-A-2011-142788, when the structure is different between a coil end provided on one end side of a stator core and a coil end provided on the other end side thereof, it is difficult to uniformly cool the one end side and the other end side of the stator core.